#include <iostream>

int main() {
    int x,y;
    scanf("%d%d",&x,&y);
    int sum;
    if (x<y){
        for (int i = x+1; i < y; i++) {
            if (i%2 != 0){
                sum += i;
            }
        }
    } else{
        for (int i = y+1; i < x; i++) {
            if (i%2 != 0){
                sum += i;
            }
        }
    }
    printf("%d",sum);
    return 0;
}
